In an opinion piece published Tuesday in the Sydney Morning Herald and other Australian newspapers, Gillard says lawmakers "should be free to vote in Parliament according to their own values and beliefs."

However, Gillard quickly came under attack from same-sex marriage advocates, who claim the prime minister is endorsing a vote she knows is destined to fail in order to keep the status quo.

Currently, three Australian states recognize civil unions, which entitle same-sex couples to the same federal benefits as married couples. Recent polls indicate a majority of Australians favor allowing same-sex marriage.